As a gas analysis apparatus adapted to measure the concentration of a measurement target component contained in sample gas such as an exhaust gas of an internal combustion engine, there is one using an infrared absorption method.
It is known that when measuring the concentration of a measurement target component (e.g., carbon monoxide (CO)) using the infrared absorption method, another gas component (e.g., carbon dioxide (CO2)) coexistent with the measurement target component in sample gas exerts a coexistent effect.
The coexistent effect is considered to occur due to the fact (broadening phenomenon) that wavenumbers are shifted by the intermolecular interaction of the coexistent component to thereby broaden the linewidth of the infrared absorption spectrum of the measurement target component broadens, and consequently the infrared spectrum changes into a broad shape.
In the past, as a gas analysis apparatus capable of removing the coexistent effect, there has been a gas analysis apparatus disclosed in Patent Literature 1. This gas analysis apparatus determines a sensitivity adjustment coefficient using the average concentration of a coexistent component in an actual sample for calibration.
However, since the gas analysis apparatus determines a sensitivity adjustment coefficient using the average concentration of a coexistent component in an actual sample for calibration, when measuring gas having different coexistent component concentration from that at the time of the calibration, an error due to the coexistent effect occurs. Further, in the case of measurement during which coexistent component concentration changes every moment as well, the coexistent effect of a coexistent component cannot be exactly eliminated.